Lecture 30 Flashcards

1
Q

How are heavy and light chain gene families encoded

A

On separate chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is somatic recombination

A

The process by which B cell segments are rearranged to create different possible antibodies
Tightly regulated
Many of the same proteins involved in DNA repair

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Genes in Light chain

A

V, J, C
Variable region, Joining region, and Constant region genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Genes in Heavy chain

A

V, D, J, C
Variable region, Diversity region, Joining region, Constant region gene
D–>only in Heavy chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where are CDR 1 and 2 encoded

A

In V segments of light and heavy chains
Both V regions are in germline DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where is CDR3 encoded in heavy and light chains

A

Heavy chain–>V, D, J gene segment
Light chain–> V-J segment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Types of light chains

A

Kappa and lambda chains
Only 1 chains will be expressed while silencing the other
2 Loci

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How many loci in Heavy chain

A

1
Different constant regions represent different isotypes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Overall pathway for somatic recombination

A

Inherited stem cell (B cell precursor)–>somatic recombination–>recombinase proteins join separate gene segments together–>mature naive B cell
Irreversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How many V regions to chose from

A

46

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How many D regions to chose from

A

23

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How many J regions to chose from

A

6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is combinatorial diversity

A

Diversity that results in different combinations of V, D, and J regions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do Recombination signal sequences (RSSs) do

A

RSSs flank each antibody gene segment to then be recognized be Recombinase enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does each Recombination signal sequence (RSS) contain

A

Nonamer (9bp) and heptamer (7bp) sequence with either a 12 OR 23 bp spacer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the 12/23 Rule

A

That 12bp RSS MUST pair with a 23bp RSS for recombination to occur

17
Q

What pairing does RSS direct in light and heavy chains

A

Light chain–> V-J
Heavy chain–> D-J and V-DJ

18
Q

What is within the Loop of DNA formed after RSS regions are brought together

A

Segments that were not selected
In loop–>out of segment

19
Q

Function of RAG-1 and RAG-2

A

RAG= recombination activating gene
Recognizing and cutting DNA at the immunoglobulin-encoding region and the RSS
Necessary for recombination

20
Q

Structure of RAG

A

Covalently closed DNA hairpin ends

21
Q

What is the signal joint

A

Loop of DNA excised when RSS are brought together
No longer on chromosome–>deleted

22
Q

What is the coding joint

A

Coding region of selected V and J regions that remain (not in loop)

23
Q

What is junctional diversity

A

When nucleotides are added or removed at junctions between V-D and D-J (or V-J for the light chain)
Occurs during recombination

24
Q

What is Artemis

A

Endonuclease that opens the DNA hairpins during junctional diversity

25
Main mechanism of Junctional Diversity
Hairpin cleavage
26
Ways that a hairpin can be opened (cleaved)
1) Exonuclease activity to remove nucleotides on each side of coding gene 2) Addition of palindromic (P) nucleotides at overhangs 3) Terminal Deoxynucleotidyl Transferase (TdT), can add up to 20 N-nucleotides (non-template encoded) to cleaved stranded mainly in heavy chain
27
Function of repair enzymes in Junctional diversity
Trim off non-matching nucleotides, Fill in remaining single-stranded gaps Ligate new DNA